The Unimog Dual-mode Road-Railer

September 20, 2006 The potential benefits of an affordable dual-mode road-rail vehicle are immense and we’ve featured previous concept vehicles in this vein from Hokkaido, Toyota (a very clever hybrid eco-friendly transit system) and Silvertip Design’s stunning Bladerunner. Now Unimog special-vehicles division has taken the wraps off a production road-railer at the Innotrans 2006 show in Berlin. Unimog’s exhibit features eight road-railer models illustrating numerous implementation scenarios on both road and rail. These include a Unimog road-railer for cost-effective shunting or manoeuvring of hauled loads of up to 1000 tonnes, a vehicle equipped with an access-platform for overhead-line maintenance and an auxiliary vehicle with crew's quarters and hydraulic equipment for rerailing derailed wagons. The vehicles are equipped with hydraulically lowerable guide wheels, with the drive on the rails being provided by the vehicle's wheels. A broad range of special railway equipment is optionally available for the Unimog road-railer, including an inductive train control system.

“In our view, the use of road-railers will become increasingly prevalent over the coming years,” explains Holger Doth, who is responsible for the road-railer segment at DaimlerChrysler AG. “That’s why we see the Innotrans 2006 show as the perfect platform for presenting our product range to an international audience of specialists.”

Advantages and capabilities of the Unimog road-railer

It uses its immense tractive power to shunt or manoeuvre heavy hauled loads, clears snow from rails and roads, grinds rail tracks, cleans tunnels, cuts clearances and maintains overhead lines. And it is highly flexible thanks to an ability to transfer rapidly between road and rail. The Mercedes Benz Unimog is capable of all this and much more. Plus it makes sound economic sense: in terms of both purchase price and running costs, it is far superior to its track-bound counterparts.

The compact design of the axle and the special-purpose wheels and rims make the Unimog ideal for use on both conventional or wide-gauge tracks (1435 to 1676 mm). On the rails, it is driven directly by the vehicle’s wheels; the guide wheels are only used to prevent derailing at speeds of up to 50 km/h. The advantage here is that the Unimog can fully utilise the high friction coefficient between the rubber wheels and the steel track. A finely graduated transmission system with eight forward and reverse gears, permanent all-wheel drive and differential locks ensure optimum transfer of the engine power (175 kW/238 hp) into maximum pulling power on the rails and enable shunting with a hauled load of up to 1000 tonnes at a speed of up to 25 km/h in both directions. A hydrodynamic torque converter, which multiplies the starting torque by a factor of 2.5, ensures smooth moving-off when towing or shunting heavy loads.

The Unimog is also optionally available with radio remote control, allowing the operator to carry out coupling and decoupling work without the assistance of a second person. Furthermore it is possible to control the Unimog from the head of the train when shunting in reverse mode, without the need for a second driver in the cab.

On-tracking made easy

The Unimog road-railer is able to quickly reach its destination by road and then transfer to the track at an embedded rail section of around five metres in length (e.g. a level crossing). As soon as the vehicle is positioned correctly, the guide wheels are lowered hydraulically – and that’s all there is to it. It takes less than three minutes for the Unimog to get ready for action on the track.

That is not the limit of this Unimog's capabilities, however; at suitable points, it can also be transferred to an open section of track. This is possible thanks to a hydraulic turntable. Furthermore, all-wheel drive and differential locks enable the Unimog to be transferred to the track even at access points in difficult terrain. After completing its work on the rails, the Unimog can be moved back onto terra firma just as quickly before being driven on to the next job site.

Implement carrier and shunting vehicle in one

Whether it is used purely as an implement carrier or as a shunting vehicle with additional attachments and superstructures (such as a crane, a snow-plough or a front arm with a mower), there are virtually no limits to the Unimog road-railer's capabilities. This is due to its design as an implement carrier with multiple attachment and mounting areas as well as integral, standardised interfaces for driving and controlling implements. A front-mounted mechanical PTO with an output of 150 kW is used to power the implements. Further power take-off points are provided on the engine and transmission. Plus there are up to four separate hydraulic circuits available. Customers also appreciate the speed of the implement changes: thanks to the innovative Unimog quick-change system, the implements can be swapped over in double-quick time.

Summary of the Unimog road-railer's benefits

Cost-effectiveness: whether it be the initial purchase cost, running costs or service costs, the Unimog makes sounder economic sense than a conventional shunting locomotive

Tractive power: shunting work with loads of up to 1000 tonnes; smooth starting-off thanks to a torque converter clutch

Transfer to and from rail tracks: rapid transfer to an embedded track section of just five metres in length; at suitable points, the Unimog can also be transferred to a non-embedded section of track using the hydraulic turntable

On the track: speeds of up to 50 km; shunting in forwards or reverse mode at up to 25 km/h; copes with curve radii starting at 18 metres

Ride comfort and ease of use: radio remote control for cost-effective one-man operation; excellent visibility at the front and in all the working areas; ergonomically designed workplace

Systems expertise: all-encompassing solution comprising vehicle and implements from a single source thanks to long-standing partnerships with leading international attachment and body manufacturers

Versatility: up to four attachment zones for implements; working hydraulics and mechanical PTOs available ex factory; suitable speed range for all operating scenarios

Service: Unimog service available at over 1000 service outlets world-wide; lifecycle support provided by the Mercedes Benz dealer network

A total of eight Unimog models and an Econic will be on display. All the vehicles are equipped with a rail guidance system and are displayed on four parallel sections of railway track.

U 400 shunting vehicle for two track gauges

One particular highlight of this Unimog road-railer is the adjustable guide wheel system which enables operation on both normal-gauge (1435 mm) and Russian-gauge (1524 mm) tracks. Equipped with a torque converter clutch, waggon brake system, coupling rod and ballast weights, this is a professional shunting vehicle capable of handling loads of up to 1000 tonnes.

U 400 with lifting platform

This Unimog road-railer boasts an access platform with a working radius of 6.5 metres and can be operated up to a height of 10 metres without requiring additional support legs. The vehicle can also be operated from the platform using the Unimog’s hydrostatic drive system. A special feature of this vehicle is the hydraulic turntable which makes it possible to access the rails even at non-embedded rail sections. The vehicle is positioned perpendicular to the track, raised using the lifting device of the turntable, rotated through 90° and then lowered onto the track with the guide wheels extended.

U 400 working and shunting vehicle

This Unimog U 400 road-railer is equipped with a guidance-bogie – a track guidance system which pivots at the centre of the axis with a guide wheel in front of and behind each Unimog wheel – for coping with very small curve radii. The Unimog also features an inductive train control system (Indusi), a "dead man's handle" and a mobile railway radio telecommunications system (Mesa). It holds certification in compliance with EBO (German railway construction and operating regulations) and BOStrab (German regulations governing operation of light rail transit systems). The crane superstructure, coupling rod and waggon brake system make this a truly all-purpose vehicle.

Two Unimog models and a Mercedes-Benz Econic are on display at the Zweiweg-Schneider stand:

U 400 shunting vehicle with buffer frame

The buffer frame of the Unimog U 400 shunting vehicle completely absorbs impacts from waggons at a speed of up to 5 km/h and a weight of up to 300 tonnes. Therefore it is also suitable for shunting waggons carrying liquids as it allows optimum absorption of the forces created by the sloshing fluid in half-empty tanks. The buffer frame enables the Unimog road-railer to be positioned in the middle of a train. In spite of the attachments for rail use, the vehicle is still highly suitable and officially approved for road use.

The Unimog U 400 with a rigid trailing axle has an increased permissible gross vehicle weight of 16.5 tonnes. The second rear axle can be hydraulically locked to enhance stability. This Unimog features a railway waggon brake system for 400 tonnes (24 axles). The loading crane superstructure (PK 16502) has a range of 6.1 to 12.6 metres, four-strut support with supporting-leg monitoring, a swivelling-range limiter and radio remote control. The working basket is designed for two persons and equipment weighing up to 300 kg.

Mercedes-Benz Econic 1828 LL vehicle for overhead-line installation

The road railer version of the Mercedes-Benz Econic has a low-floor cab, enabling easier access and egress at construction sites. The vehicle features a dual-axle hydrostatic drive system with an axial piston-type variable-displacement pump for operations on metro or tramway lines with small curve radii. The Econic can be operated from the platform and also features an extended cab with an integrated workshop area.

Three Unimog road-railer models are on display at the Zagro/Zwiehoff stand:

U 400 shunting vehicle

This is a shunting vehicle equipped with a torque converter clutch, a waggon brake system for 52 axles (max. 800 tonnes), an automatic coupling rod with lifting device, a UIC coupling head and a camera system for easy on-tracking including illumination of the rail guidance system.

U 400 recovery vehicle

This Unimog U 400 can be employed for operations such as rerailing derailed waggons. It features a box body with integrated crew compartment and sufficient stowage capacity for necessary tools. The rerailing system includes a hydraulic assembly driven by the Unimog's front PTO shaft as well as various lifting cylinders and rerailing bridges. Spreaders, cutting and welding equipment, floodlights and a three-phase generator are available for rescue operations. The ability to approach the operating site by road and carry out on-tracking practically on the spot make the Unimog road-railer the ideal choice when time is of the essence.

U 400 with road-rail trailer

This Unimog road-railer with a crane, a front arm with a branch-cutter and a road-rail tandem-axle trailer can perform a number of railway infrastructure-related tasks. These include cutting clearances, mowing embankments, exchanging sleepers or switches and towing waggons carrying materials to trackside construction sites. Even with a road rail trailer, the vehicle can easily be lifted onto tracks at a level crossing, for example. And it can be driven to the next operating site quickly and cost-effectively by road.

After Editing or Managing over 50 print publications primarily in the role of a Magazine Doctor, Mike embraced the internet full-time in 1995 and became a "start-up all-rounder" – quite a few start-ups later, he founded Gizmag in 2002. Now he can write again. All articles by Mike Hanlon